It is known that power transformers, for example with a rated power of a few MVA and in a voltage range of 5 kV to 30 kV or 110 kV, sometimes even up to 170 kV, for example, are also in the form of dry-type transformers, wherein, in the last-mentioned voltage range, rated powers of 50 MVA and above are also entirely possible. During operation of a transformer, lost heat is produced in the electrical windings of the transformer, and this lost heat should be dissipated to the surrounding environment. Therefore, at least one cooling channel guided along the axial extent of the winding is developed in order to pass the lost heat, e.g., by means of natural air cooling, out of the winding interior, in order to cool such a dry-type transformer. In order to increase the cooling effect the radially inner low-voltage winding is divided into a plurality of radially spaced-apart, hollow-cylindrical winding segments which are connected electrically in series and between which a likewise hollow-cylindrical cooling channel is arranged.
However, one disadvantage with this is that the (stray) capacitance of the interconnected winding is no longer distributed approximately homogeneously amongst the individual winding turns, but instead a region with a low capacitance is developed in the region of the cooling channel. The result can be realized in dry-type transformers because the cooling channels provided there have a thickness of a few centimeters. On the other hand, in oil-filled transformers, the thickness of the cooling channels is in the millimeters range, with the result that the capacitive change in the winding is correspondingly small.
This effect can be important under the conditions of surge voltage loading of the winding, e.g., in the case of a voltage pulse entering from the outside at the terminals of the winding, for example with a rise time in the μs range. Owing to the high-frequency fundamental component of such a voltage pulse, the voltage is distributed along the individual turns of the winding corresponding to the respective capacitance thereof. Since the capacitance is now distributed non-uniformly owing to the introduction of the cooling channel, a disadvantageous non-uniform voltage loading of the conductor also results, which conductor can be designed for the same voltage loading over its entire length.
Against the background of this prior art, the object of the disclosure is to specify a transformer winding with a homogenized voltage distribution in the case of surge voltage loading.